Thermal release device



Patented May 19, 1931 UNITED STATES- PATENT OFFICE ERNST BESAG, OFBADEN-IBADEN, GERMANY, ASSIGNOR TO SCHIELE & BRUCHSALER INDUSTRIEWERKEA. G., OF BADEN-BADEN, GERMANY THERMAL RELEASE DEVICE At present thereare employed, particularly in switch constructions, thermal releasedevices in which a heating wire on a definite current strength beingreached causes a fusible mass to soften after expiry of a definiteinterval of time as a result of which a toothed rotatable element of therelease deviceisreleased and a spring controlled pawl moves out ofengagement with the toothed portion and by its movement effects arelease of the switch.' Known releasing devices of this kind arecomparatively complicated and require. comparatively high heatingenergy, namely 1 or 2 watts and moreover suffer from the dis advantagethat even although built to the same dimensions no two devices releaseafter the same time interval with a given current strength.

These disadvantages are avoided by the invention, the essential featureof which consists in this that a rotatable hollow body filled withfusible material is directly mounted on the heating body, at least apart of which is in the form of a wire and a portion of which extendsradially within the hollow body.

In the accompanying drawings which illustrate two embodiments of theinvention,

Fig. 1 illustrates a release device in wh1ch the heating wire has theshape of a crank shaft and Fig. 2 is a section on the line AB of Fig. 1.Fig. 3 shows a thermal release device of a preferred construction.

Referring to Fig. 1, the heating wire 1 carries a drum 2 or other hollowbody which is formed or provided with teeth 3. .The'interior 4 of thedrum 2 is filled with a fusible mass preferably an eutectic alloy. Thewalls bounding the space 4 are made other than cylindrical so that thedrum 2 cannot rotate when the fusible mass is in cold condition. Whenthe heating wire 1 reaches a definite temperature the mass i melted andthe drum 2 is free to rotate. a portion of the heating wire 1 formed asa crank shaft describing a surface of revolution within the fusedmaterial. In a releasing device as shown in Figs. 1 and 2 of which thegreatest dimension amounts to fractions of a centimetre, results328,811, and in Germany December 28, 1927.

can be obtained with a heating energy of about 0.6 watts.

In the embodiment shown in Fig. 3 in which the several parts areindicated by the same reference numerals as are employed in Figs. 1 and2, the heating wire 1 is shaped as a crank shaft the cranked portion ofwhich has been twisted through 90.

I claim,

1. In a thermal release, a resistance wire, a drum directly supportedthereon, the resistance wire extending therethrough, fusible materialfilling said drum, the wire having a radially directed portion, the saidmaterial embedding the portion of the wire which is within the drum andalso the said radially directed portion thereof, whereb to normallyprevent rotation of the rum and whereby the fusing'of the said materialby heating of the wire upon the passage of an abnormally high currentwill permit the rotation of the drum. I

2. In a thermal release, a resistance wire,

a drum directly supported thereon, fusible fusing of the said materialby heating of the wire upon the passage of an abnormally high currentwill permit the rotation of the drum.

3. In a thermal release, a substantially unitary resistance wire, a drumdirectly supported thereon, the resistance wire extending therethrough,fusible material filling said drum, the portion of the wire which iswithin the drum being formed to provide a cranked radially directedportion, the said material embedding the said portion of the wire whichis within the drum and also the said cranked radially directed portionthere-1 4. In a thermal release, a resistance wire,

a drum directly supported thereon, fusible material filling said drum,the portion of the wire which extends within the drum, in a portion ofits length being bent to form to simulate a substantially U-shaped crankshaft and having its said last-mentioned portion disposed in a plane atright angles to the axis of the said portion of the wire I which extendswithin the drum, whereby to normally prevent rotation of the drum andwhereby the fusing-of the said material by heating of the 'wire upon thepassage of an abnormally high current will permit the rotation of thedrum.

5. In a thermal release, a resistance wire, a drum directly supportedthereon, the said drum having a polygonal shaped interior wall, fusiblematerial filling the said drum,

the said resistance wire extending through the said drum, the portion ofthe said wire which is within the drum being iormed with a substantiallyU-shaped off set portion and having the said lattervportion disposed ina plane substantially at right angles to the axis of that portion of theresistance wire which extends within the drum, whereby to normallyprevent rotation of the drum and whereby the fusing of the said materialby heating of the wire upon the passage of an abnormally high currentwill permit the rotation of the drum.

In testimony whereof I-have signed my name to this specification.

ERNST BESAG.

